This invention relates to an electron emission element usable in various apparatus such as an electron microscope, an electron beam exposure apparatus, a cathode-ray tube (CRT), or other electron beam apparatus.
Recently, electron emission elements dispensing with a heating process have been widely studied. Typical examples of such electron emission elements are field emitters and micro-field-emitters.
A general field emitter includes an emitter tip which is made into a needle shape so as to have a curvature radius of several hundreds of nanometers or smaller. An electric field having a strength of about 10.sup.7 V/cm is concentrated on the emitter tip, forcing electrons to be emitted from the emitter tip. Such a field emitter has advantages, that is, (1) a high current density and (2) a low power consumption.
As will be explained later, a background-art electron emission element has some problem.